It really shouldn't be a surprise that a team that won 99 games overall (.611 winning %) was .650 in one-run games.

Well that's kind of a chicken and egg argument; did the Sox win 65% of their 1-run games because they were a 99-win team or were they a 99-win team because they won 65% of their one-run games?

1-run game win percentage has proven to be EXTREMELY volitale figure. A 65% WP (which, FWIW, is a 105-57 record over a 162-game season) is an insanely high winning percentage. You can't rely on or expect a team to repeat that kind of performance year in and year out. Generally speaking, a team's "blow out" win percentage is a much more reliable indicator of their level of talent. The '05 Sox were 21-16 in "blowout games," a .568 winning percantage which would have been a 92-70 record in a 162-game season.